Behavior in the presence of kerning and ligature

[Didier Verna]

  Hello,

I have a question regarding what TeX does when faced with both ligature
and kerning information at the same point.

If I do something like this:

Mff
M\kern-2ptff
M\kern-2ptf{}f

I see that my explicit kerning instruction is always honored, which is
normal.

But my question is this: suppose a font has a special kerning between
characters A and B, and also a ligature between B and C (giving L), and
suppose my input is ABC. What happens?

Possibilities:
1. kern is applied, then ligature is created: A (kern) L, but this could
   be regarded as wrong because the kern wasn't really about A and L,
2. ligature is applied so that the input is AL, and there's no kerning
   between those, except that it feels in contradiction with the way
   characters are eaten,
3. that situation should never happen in a font,
4. bell rings, pizza gets delivered.

Thanks.

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